NUMERICAL ANALSIS ON CONVECTION HEAT TRANSFER OF PULSTING FLOW IN A CORRUGATED TUBE

摘要

Heat transfer enhancement of corrugated tube in Laminar flow was studied using CFD. Numerical calculation performed with grids of increasing density confirms that the grids are independent. In order to get the optimal numerical calculation the boundary layer was refined. The final grid consisted of 146,000 computational cells. The fluid inlet was defined as a velocity inlet with a sinuaoidal pulasating flow input. The outlet was modeled as a pressure-outlet.By numerical simulation, the distribution of velocity and temperature of the corrugated tube of different conditions in different Reynolds number(380~1900) of steady flow ,and the vibration frequency (50-200HZ)and the vibration amplitude of sinusoidal (0.1—0.9) pulsating flow is analysed, thus the characteristics of distribution of velocity and temperature are demonstrated. Thesimulation result indicates that by comparing with the steady flow, the pulsating flow increases the heat transfer efficiency of the corrugated tube in Laminar flow by 83% for most. The enhancement is due to the pulsating flow increating vortex. The vortex result in increasrs disturbance, decreasing the thermal boundary layer thickness, enhancing heat transfer of the corrugated tube. The result also shows that enhancement of heat transfer coefficient inceases as the velocity rises in a certain range ,and it also increases as the frequency rises before reaching the peak point and then decreases as the vibration frequency rises in a certain range. Under the condition of none-backflow, the velocity of increasing enhancement of heat transfer coefficient becomes slower and slower as the vibration amplitude rises. In our study, the best dimensionless pulsating frequencies of thecorrugated tube are 100-200 HZ and the amplitudes are 0.4~0.6 , when condition that the Reynolds number is ranged from 380 to 1900.